Dynamic forward error correction bypass in a digital communications system

ABSTRACT

A system and method of improving communications is provided. A gateway is communicatively coupled to an end terminal through an unmanned air vehicle (UAV), wherein a first link communicatively couples the gateway to the UAV, and a second link communicatively couples the UAV to the end terminal. At least one of the gateway and the UAV is configured to determine a signal quality on at least the first link between the gateway and the UAV in a first direction. If the signal quality exceeds a predetermined threshold, a received packet is encoded at the gateway for processing by the end terminal. The packet is further tagged with an indicator that the packet should bypass forward error correction (FEC) at the UAV.

BACKGROUND

In digital communications systems, such as those based on unmanned airvehicles (UAVs), the system may have greater capacity when less power isrequired by the digital payload. Moreover, a greater coverage area maybe provided when less power is required. One of the greatest powerconsumers on the UAV is a receiver function of digital modems. A forwarderror correction (FEC) decode function block consumes a large amount ofpower. However, the FEC decode function block maintains the overall biterror rate (BER) and link performance.

A UAV supports user links, gateway links, and inter-UAV links. The FECdecoder is a large consumer of power for all of the wireless links.There is one FEC decoder allocated to each wireless link. There are alarge number of user links since there is one user link for each user.There can be as many as 100s of active user links. There are typically asmall number of gateway and inter-UAV links, on the order of 1 to 10.

BRIEF SUMMARY

One aspect of the disclosure provides a method of improvingcommunications. The method includes receiving a first packet at agateway communicatively coupled to an end terminal through a UAV,wherein a first wireless link communicatively couples the gateway to theUAV, and a second wireless link communicatively couples the UAV to theend terminal. A signal quality on at least the first link between thegateway and the UAV in a first direction is determined with one or moreprocessors. If the signal quality exceeds a first predeterminedthreshold, the first received packet is encoded at the gateway forprocessing by the end terminal. Moreover, the first received packet istagged with an indicator to bypass FEC at the UAV. In some examples, themethod may further comprise receiving, at the gateway, a second packetfrom the UAV, the second packet originating from the end terminal,determining, with the one or more processors, whether the second packetwas FEC decoded and encoded at the UAV, and if it is determined that thesecond packet was not FEC decoded and encoded at the UAV, decoding thesecond packet at the gateway using end terminal modem processing.

Another aspect of the disclosure provides a gateway. The gatewayincludes an interface adapted to be communicatively coupled with a UAVover a first link and with at least one end terminal over a second linkbetween the UAV and the at least one end terminal. The gateway furtherincludes at least one FEC encoder adapted to be interfaced with abackhaul and to receive a first packet from the backhaul, a formattingunit coupled to the FEC encoder, and a controller communicativelycoupled to the at least one FEC encoder and the formatting unit. Thecontroller is configured to determine whether the signal quality overthe first link exceeds a first predetermined threshold. If the signalquality is determined to exceed the first predetermined threshold, thegateway switches from a first mode to a second mode. In the second mode,the at least one FEC encoder is configured to encode the received firstpacket for processing by the end terminal, and the formatting unit isconfigured to tag the received first packet with an indicator to bypassFEC at the UAV.

Yet another aspect of the disclosure provides a UAV, comprising a firstinterface adapted for receiving a first packet from a gatewaycommunicatively coupled to the UAV via a first wireless link, and asecond interface adapted for receiving a second packet from an endterminal communicatively coupled to the UAV via a second wireless link.The UAV further includes a FEC encoder coupled between the firstinterface and the second interface, a FEC decoder coupled between thefirst interface and the second interface, and a bypass link coupledbetween the first interface and the second interface and bypassing theFEC encoder and the FEC decoder. Moreover, the UAV includes a controllerin communication with at least the first interface and the secondinterface, the controller configured to determine whether the firstpacket has been encoded for end terminal processing, and cause the firstpacket to be sent on the bypass link if it has been encoded for endterminal processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system transmitting in a firstdirection according to aspects of the disclosure.

FIG. 2 is a block diagram of another example system transmitting in thefirst direction according to aspects of the disclosure.

FIG. 3 is a block diagram of another example system transmitting in thefirst direction according to aspects of the disclosure.

FIG. 4 is a flow diagram of a transition between modes according toaspects of the disclosure.

FIG. 5 illustrates an example packet format according to aspects of thedisclosure.

FIG. 6 is a block diagram of an example system transmitting in a seconddirection according to aspects of the disclosure.

FIG. 7 is a block diagram of another example system transmitting in thesecond direction according to aspects of the disclosure.

FIG. 8 is a block diagram of another example system transmitting in thesecond direction according to aspects of the disclosure.

FIG. 9 is a block diagram of an example system including inter-vehiclelinks according to aspects of the disclosure.

FIG. 10 is a block diagram of an example gateway terminal according toaspects of the disclosure.

FIG. 11 is a block diagram of an example UAV according to aspects of thedisclosure.

FIG. 12 is a flow diagram illustrating an example method of FEC bypassin a transmit direction according to aspects of the disclosure.

FIG. 13 is a flow diagram illustrating an example method of FEC bypassin a receive direction according to aspects of the disclosure.

DETAILED DESCRIPTION

According to this disclosure, the FEC decoder function is dynamicallyremoved from the UAV on all of the user links, gateway links, andinter-UAV links. Accordingly, power consumption in the UAV issignificantly reduced. The dynamic removal of the FEC decoder functionis based on instantaneous link quality, such as Bit Error Rate (BER) orFrame Error Rate (FER), and other parameters, such as available powerand estimated future power consumption. When the wireless links in theUAV based system are very high quality, FEC decoders may be removed fromthe UAV with little to no impact on the overall Bit Error Rate. In someexamples, depending on the link details, the FEC decoder function ismoved from the UAV to a gateway terminal during high signal qualityconditions. When signal quality is low, in order to achieve the highestradio link quality and lowest BER possible, the FEC decoders are notbypassed, thus providing the highest protection. It is anticipated thatthese events with low signal quality will be of short duration, thus thehigher power required for this mode will only be over a short amount oftime. A background power allocation algorithm is used to determineexactly when to operate in which mode. This background algorithm makesthe trade-offs between acceptable BER rates, and power consumption, andanticipated usage for the next few hours, and thus anticipated powerneeds.

FIG. 1 shows a “forward” data-path for a UAV system, where data isflowing from gateway terminal 120 towards an end user terminal 190through UAV 150.

The gateway terminal 120 may reside on, near, or under ground. Thegateway terminal 120 includes, for example, FEC encoder 122, modem frontend unit 124, digital to analog (D/A) converter 126, and radio frequency(RF) front end unit 128. As shown, the gateway terminal 120 has abackhaul connection to the Internet. For example, a fiber opticconnection may be established between the gateway terminal 120 and anInternet access point. Data from the Internet enters the gatewayterminal 120 and then goes to FEC encoder 122.

Data is transmitted from the gateway terminal 120 to the UAV 150 viawireless gateway link 140. The UAV 150 includes, for example, analog todigital (A/D) converter and RF front end unit 152 which receives datatransmissions from the gateway terminal 120 over the wireless gatewaylink 140. The UAV 150 may further include FEC decoder 154 and FECencoder 156, which may be selectively utilized based on, for example, aquality of the signal between the gateway terminal 120 and the UAV 150,as discussed further below. The UAV 150 further includes modem front end158, D/A converter 160, and RF front end 162. The RF front end 162 maybe an interface used for transmitting data from the UAV 150 to the userterminal 190 over wireless user link 180.

Some components of the UAV 150 perform tasks which are part of gatewaylink modem/FEC format processing. For example, A/D and RF front end unit152 and FEC decoder 154, we well as each of the components 122-128 ofthe gateway terminal, perform gateway link modem/FEC format processing.Other components of the UAB 150, such as components 156-162, and userterminal 190 perform tasks which are part of user equipment (UE)modem/FEC format processing.

The UAV 150 may be, for example, a satellite, a solar cell tower, anaircraft, or any other type of air vehicle containing communicationsequipment. While the gateway terminal 120 is fixed in position, the UAV150 may be moving around in the air. Accordingly, at some times a lineof site between the gateway terminal 120 and the UAV 150 will be lessobstructed than at other times. Changes in line of sight and otherconditions, such as weather, may affect a signal quality of datatransmissions over the wireless gateway link 140.

The user terminal 190 may be, for example, a full-sized personalcomputer, or a mobile device capable of wirelessly exchanging data withthe UAV 150. By way of example only, user terminal 190 may be asatellite phone, a wireless-enabled PDA, a cellular phone capable ofobtaining information via the Internet, etc. The user terminal 190 mayalso move about. At some times, for example, the user terminal 190 maybe outside under a clear sky, and have a direct high quality wirelessconnection with the UAV 150. In other examples, however, the line ofsight between the user terminal 190 and the UAV 150 may be obstructed,for example, by buildings, trees, other structures, clouds, rain, orother weather conditions. Accordingly, a quality of signals transmittedbetween the UAV 150 and the user terminal 190 may be lower.

Packets transmitted between the gateway terminal 120 and the userterminal 190 through the UAV 150 may be handled differently based onsignal quality. In determining signal quality, an aggregate quality overall links may be considered. For example, an aggregate bit error rate ofsignals over gateway link 140 and also of signals over user link 180 maybe computed. The signal quality may also be determined in both transmitdirections—from the gateway 120 to the user terminal 190, and also fromthe user terminal 190 to the gateway 120. In other examples, the errorrate of only some links and/or in only one direction may be considered.

When signal quality is relatively high, such as above a predeterminedthreshold, the UAV FEC decoder 154 and FEC encoder 156 may be bypassed.Accordingly, packets encoded by the gateway FEC encoder 122 are providedto the end user terminal 190, where they may be decoded. Bypassing theFEC decoding/encoding in the UAV 150 may significantly reduce powerconsumed by the UAV 150. Because signal quality is high, the bit errorrate (BER) is low, and thus bypassing FEC decoding and encoding in theUAV 150 will not significantly impact signal quality. When quality ofsignals between the gateway terminal 120 and the UAV 150 is relativelylow, such as below the predetermined threshold, FEC decoding andencoding in the UAV 150 may be performed, thereby maintaining a reducedBER. The determination of whether or not to bypass the FECdecoding/encoding in the UAV 150 may be made dynamically by, forexample, a controller (not shown) in the gateway terminal 120 or the UAV150.

FIG. 2 illustrates the aforementioned bypass of the FECdecoding/encoding in the UAV 150. Under good signal quality conditions,the FEC Encoder 122 does not perform forward error correction overgateway link 140, but rather performs forward error correction for userlink 180. According to the example shown in FIG. 2, The UAV sends thepackets along FEC bypass link 270 when good signal quality conditionsare present. According to other examples, the packets may be transmittedthrough the FEC decoder 154 and FEC encoder 156 without being processed.When good signal quality conditions are present, the BERs on the forwardpath from the gateway terminal 120 to the UAV will be very low, but notnecessarily zero. The BER may be low enough that an FEC decoder in theuser terminal 190 will correct the errors with no significant impact onthe end-to-end BER. The FECs for each type of link can be completelydifferent or exactly identical, and can still be supported by the system100. Also, in some examples, the forward FEC encoding function may beperformed in a ground switching center, such as in the cloud.

Packets encoded by the FEC encoder 122 for the user link 180 may beformatted and tagged so the UAV 150 knows that it should bypass FECdecoder 154 on the gateway link 140, as well as FEC encoder 156 towardsthe user link 180. The tag may be, for example, a small header for eachframe. This tag may be protected, for example, with parity bits or asmall FEC block. The tag indicates to bypass the FEC decode/encodeblocks and indicates on which user link to transmit. For example, thetag may specify a particular beam, frequency, and timeslot on which totransmit the accompanying packet. While in some examples each FEC blockwill require a tag, in other examples a set of FEC blocks together couldrequire one longer tag for more efficient FEC. In some cases, the tagwill serve as an index to a table that identifies the particular beam,frequency and timeslot, so as to minimize the size of the tag.

FIG. 3 provides a more detailed illustration of the forward or transmitpath through a system 300. As shown, gateway terminal 320 includes FECencoder 322, modem front end 324, D/A converter 326, and RF front end328, similar to the description of gateway terminal 120 above. Alsoshown in FIG. 3, gateway terminal 320 includes a second FEC encoder 332and a formatter and tagger 334 performing UE modem/FEC formatprocessing. When signal quality between the gateway 320 and UAV 350 ishigh, the FEC encoder 332 may be utilized to encode packets for an enduser link, and formatter and tagger 334 may configure the packet toinclude an indication that FEC decoding/encoding should be bypassed.

The gateway terminal 320 also includes gateway controller 330. Thegateway controller 330 may determine the quality of the signal betweenthe gateway 320 and the UAV 350. For example, the gateway controller mayperiodically or continually monitor a BER of packets sent over gatewaylink 340. The packets used to make this determination may be actual datapackets or test packets. In some examples, information received backfrom the UAV 350 may be used in determining the quality of signals overthe link 340. For example, UAV controller 372 or other components of theUAV 350 may provide signal quality information, such as error rate,etc., to the gateway controller 330.

Once a packet received from backhaul is encoded, either by first FECencoder 322 or by second FEC encoder 332, the packet is sent through thegateway 320 to the UAV 350 over gateway link 340. The packet is receivedat A/D and RF front end unit 352, and then provided to un-formatter 374.The un-formatter 372 may be, for example, additional hardware configuredto handle different formats of packets for different processing. Theun-formatter, in communication with UAV controller 372, may determinewhether the packet was formatted for the gateway link modem by the firstFEC encoder 322 or for UE modem by the second FEC encoder 332. Forexample, the un-formatter 374 may identify how the packet was formattedbased on information in the packet header, such as tags or user linkinformation.

If signal quality is low, and the first FEC encoder 322 encoded thepacket with gateway link modem/FEE format processing, the un-formattersends the packet to FEC decoder 354 for regular FEC decoding, and FECencoding with UE modem/FEC format processing at FEC encoder 356.However, where signal quality is high and the second FEC encoder 332 inthe gateway 320 encoded the packet with UE modem/FEC format processing,the un-formatter 374 sends the packet over bypass link 370 directly tomodem front end 358. From the modem front end 358, all packets are sentto the D/A converter 360 and the RF front end 362 for transmission to aparticular user device.

FIG. 4 is an example state machine illustrating a determination whetherto turn FEC bypassing on or off. In initial state 410, FEC bypass may beoff. In some examples this initial state 410 may also serve as thedefault state. The system remains in this state for several seconds andthen starts monitoring link quality indicator (LQI).

In this example, LQI is computed as a function of signal strength, frameerror rate, and bit error rate. In other examples, only some of thesefactors, or other factors, may be considered. The LQI in this example iscomputed based on a combination of the gateway link 140 (FIG. 1) and theuser link 180 (FIG. 1). For example, the FEC decoder 154 (FIG. 1) in theUAV 150 reports on the gateway link 140 channel quality, includingsignal strength, FER, and BER. The FEC decoder in the UE (not shown)reports the user link 180 channel quality. The reports may be sent toone or both of the UAV controller 372 (FIG. 3) and the gatewaycontroller 330 (FIG. 3) for continued monitoring of the LQI.

As long as the LQI is below a threshold T1, the FEC bypass remains off.However, as soon as the LQI improves above T1, then the FEC Bypass modeis turned on and the state changes to FEC Bypass On state 420.

In the FEC Bypass On mode 420, the state stays the same, as long as theLQI is greater than or equal to Threshold 2 (T2). T2 may be slightlylower than T1. This may minimize a ping-pong effect, where the staterapidly flips based on only very small changes in LQI right at thethreshold.

Once the LQI drops below T2, the state goes back to FEC Bypass Off mode410. Once the FEC Bypass Off state is reached again, it stays in thismode for a certain time period, on the order of a few seconds tominutes, before monitoring the LQI again. This delay in monitoring theLQI may ensure that in rapidly varying LQI conditions, the FEC Bypassstate stays in the Off state.

Since this system is a 2-way communications system, the FEC Bypassdetermination may be made independently for each direction. In otherexamples, the determination could be made for one direction with theassumption that both directions will have essentially equal or similarlink quality conditions, and thus only one direction needs to bemonitored for both directions.

In addition, the communications system may support multiple beams,multiple frequencies, or multiple users. As such, the system may haveone of these FEC Bypass state machines for the entire system, or mayhave one state machine for each beam, or frequency, or user. Moreover,the communications system may support different logical channels ortimeslots on the same frequency. Again one of these state machines maybe implemented for each logical channel or timeslot, or may beimplemented for the entire channel as a whole.

While in the example above the determination of whether to turn FECBypass mode on or off is based on a computed LSI as compared to athreshold, in other examples the determination may be based on otherfactors. For example, the determination may be based upon weather data.In such an example, a unit in the gateway or UAV may detect weatherconditions. In clear skies FEC may be bypassed in the UAV, while in anyother condition regular FEC decoding/encoding may be performed by theUAV.

In some examples, even during periods of high quality signal conditions,the system may periodically switch the FEC bypass mode to off. In thisregard, the system may collect statistics, verify accurate functioning,or perform other tasks. The periodic switching off of the FEC bypassmode could be for 1 frame per N frames where N is around 100 or so, orthis could be for a few seconds every few minutes, or for any otherfrequency.

FIG. 5 illustrates an example packet formatted for FEC bypass, forexample by the second FEC encoder 332 (FIG. 3). In this example, thepacket includes a header identifying information such as sourceidentifier, destination identifier, priority, or any other informationdepending on a type of packet or protocol. The second FEC encoder mayadd information to the header, such as a tag 505. The tag 505 may be,for example, a binary representation having any length. According tosome examples, the tag is protected by parity bits or a code block toensure proper handling by recipients of the packet. The header may alsoidentify information regarding a specific user link. For example, abeam, frequency, and timeslot may be specified in fields 510, 515, 520,respectively. Or alternatively, the header may have a tag that is anindex to a lookup table that contains the destination information suchas beam number, channel number, timeslot, and user number.

FIG. 6 illustrates transmission of data through system 600 in a returnor receive direction. In the return direction, packets are sent fromuser terminal 690 back towards UAV 650, gateway 620 and Internet. Whileonly one FEC decoder 656 is shown in the UAV 650 in FIG. 6, the UAV 650may have a large number of FEC decoders to support a large number ofusers. These FEC decoders can dynamically be moved from the UAV 650 tothe gateway terminal 620 or even further back in the network, such as ata ground switching center, for example, on a cloud processor. These FECdecoders would be moved on a per user basis, when the user signal is ofhigh quality. When the FEC decoders are moved to the ground, the FECencoder 656 on the UAV 650 towards the gateway terminal 620 is bypassed.

FIG. 7 illustrates an example where the FEC decoder 656 is moved to thegateway 620, and bypassed on the UAV 650. UAV controller 772 may be infrequent or continual communication with gateway controller 730. One orboth of the UAV controller 772 and the gateway controller 730 maymonitor signal quality on one or both of user link 780 and gateway link740, and determine, for example, whether the signal quality meets orexceeds a predetermined threshold. If the threshold is met, as packetsare received at the UAV 650 from the end terminal 690, the packets maybe directed through modem front end 758 directly to D/A and RF front end752, bypassing FEC decoder/encoder. For example, the UAV controller 772may instruct the modem front end 758 to send the packets over FEC bypasslink 770. The FEC decoding may instead be performed at the gateway 720by FEC decoder 756.

FIG. 8 illustrates a detailed example of receive direction FEC bypass ina system 800, implementing an additional power savings technique in thereturn direction. Packets received at the UAV 850 pass through RF frontend 862 and A/D converter 860. Raw I/Q samples are then sent from theA/D converter 860 to formatter and tagger unit 876. This not onlybypasses the FEC decoder/encoder, but will also bypass the modem aswell. In a typical system, the raw IQ samples are sent to the modemwhere they are demodulated into soft decision bits, and then those softdecision bits are sent to the FEC decoder. In the present example, theheader/tag of the packet is still decoded, and the data section of thepacket is left as raw I/Q samples. The benefit of this mode is that itallows for optimal decoder operation at the end user station in theforward direction, and at the gateway terminal in the return direction,since minimal information is lost due to quantizing the raw I/Q samples.However, as this technique requires more bandwidth, it is most usefulwhen the overall system demand is well below the capacity of the link.

According to another example, instead of sending “hard decision” bitsout of the modem front end 858, “soft decision” bits may be sent. The“soft decision” bits may be of variable length, depending on the signalquality. Accordingly, the soft decision bits may be provided tobit-width reducer 878, which may reduce a width of the soft decisionbits to a predetermined width. Note that the soft decision bits aredifferent then the raw IQ samples, because they have been demodulated bythe modem. For the software decision bits, the greater the bit width,the less information is lost due to quantization, however, the morecapacity and thus power is required. So the bit-width reducer iscontinually trying to minimize the bit width, and still maintain minimalquantization error to minimize the BER. For very high signal quality,and low order modulation, only a small number of bits are required, suchas 6 bits. For slightly lower signal quality cases, more bits arerequired, such as 12 to 16 bits.

Using soft decision bits increases the required capacity of the link 840down to the gateway 820. Accordingly, soft decision bits may be usedonly during low capacity times. For example, the controller 872 maymonitor a capacity of the gateway link 840. If the capacity is above apredetermined threshold, the soft decision bits may be used. Otherwise,hard decision bits may be used.

FIG. 9 illustrates an example using Inter-Vehicle-Links (IVLs). Asshown, gateway 920 is wirelessly coupled to UAV 950, which is furthercoupled to UAV 951 and UAV n. UAV n is wirelessly coupled to userequipment (UE) 990. The power saving techniques described above may beused at each hop. For example, if an aggregate LQI computed for alllinks 940, 941, 942, 980 is above a predetermined threshold, each IVL940, 941, 942, 980 can forward data with or without going through thedecode/encode functions in the UAVs 950, 951, n.

FIG. 10 illustrates an example gateway terminal 1020. The gatewayterminal 1020 may be communicatively coupled between a network, such asthe Internet, and a UAV or other communication device having powerconstraints. The UAV may be further coupled to one or more end terminaldevices, such as mobile phones, tablets, laptops, or any other mobilecomputing device.

As shown in FIG. 10, the gateway terminal 1020 can contain one or moreprocessors 1030, memory 1060 and other components typically present ingateway terminals, such as interfaces, modems, A/D and D/A converters,etc. The gateway terminal 1020 may further include other components,such as a formatter/un-formatter/tagger unit 1082, a first FECencoder/decoder 1084, and a second FEC encoder/decoder 1086. The firstFEC encoder/decoder 1084 may, for example, be used for regular modemprocessing. The second FEC encoder/decoder 1086 may be used, forexample, for end terminal processing where FEC is bypassed in the UAV.

The memory can be of any non-transitory type capable of storinginformation accessible by the processor, such as a hard-drive, memorycard, RAM, DVD, write-capable, etc. The memory 1060 can storeinformation accessible by the one or more processors 1030, includinginstructions 1068 that can be executed by the one or more processors1030. Memory 1060 can also include data 1062 that can be retrieved,manipulated or stored by the processor 1030.

The instructions 1068 can be any set of instructions to be executeddirectly, such as machine code, or indirectly, such as scripts, by theone or more processors. In that regard, the terms “instructions,”“applications,” “steps” and “programs” can be used interchangeablyherein. The instructions can be stored in object code format for directprocessing by a processor, or in any other computing device languageincluding scripts or collections of independent source code modules thatare interpreted on demand or compiled in advance.

Data 1062 can be retrieved, stored or modified by the one or moreprocessors 1030 in accordance with the instructions 1068. In oneexample, the data 1062 may include at least one predetermined signalquality threshold. The signal quality threshold may be based on BER,signal strength, or any combination of these or other quantifiers. Forexample, the threshold may be a BER of 10⁻⁶.

In accordance with the instructions 1068, the gateway 1020 may determinewhether the links connecting the gateway 1020 to the end terminal aretransmitting at high signal quality. For example, during bad weathersome links may experience an increased error rate. Where signal qualityof the links is high, the gateway 1020 may execute instructions, usingthe processor 130, to encode packets for processing by the end terminaland format/tag packets for FEC bypass in the UAV. In a reversedirection, the instructions 1068 may be executed by the processor 1030to determine whether a packet received from the UAV had bypassed FEC inthe UAV, and thus whether the packet should be sent to the first FECencoder/decoder 1084 or the second FEC encoder/decoder 1086.

Although the subject matter described herein is not limited by anyparticular data structure, the data 1062 can be stored in internal orexternal memory, computer registers, in a relational database as a tablehaving many different fields and records, or XML documents. The data1062 can also be formatted in any computing device-readable format suchas, but not limited to, binary values, ASCII or Unicode. Moreover, thedata can comprise any information sufficient to identify the relevantinformation, such as numbers, descriptive text, proprietary codes,pointers, references to data stored in other memories such as at othernetwork locations, or information that is used by a function tocalculate the relevant data.

The one or more processors 1030 can be any conventional processors, suchas commercially available CPUs. Alternatively, the processors can bededicated components such as an application specific integrated circuit(“ASIC”) or other hardware-based processor. Although not necessary, theprocessors 1030 may include specialized hardware components to performspecific computing processes.

Although FIG. 10 functionally illustrates the processor, memory, andother elements of gateway terminal 1020 as being within the same block,the processor, computer, computing device, or memory can actuallycomprise multiple processors, computers, computing devices, or memoriesthat may or may not be stored within the same physical housing. Forexample, the memory can be a hard drive or other storage media locatedin housings different from that of the gateway terminal 1020.Accordingly, references to a processor, computer, computing device, ormemory will be understood to include references to a collection ofprocessors, computers, computing devices, or memories that may or maynot operate in parallel. For example, the gateway terminal 1020 mayinclude load-balanced computing devices, a distributed system, etc. Yetfurther, although some functions described below are indicated as takingplace on a single computing device having a single processor, variousaspects of the subject matter described herein can be implemented by aplurality of computing devices, for example, communicating informationover a network.

FIG. 11 illustrates an example UAV 1150. Similar to the gatewayterminal, the UAV 1150 may include a memory 1160 including data 1162 andinstructions 1168, and one or more processors 1172 in communication withthe memory 1160 and other components. The memory 1160 and processors1172 may be any of a variety of types, similar to the memory 1060 andprocessors 1030 described above in connection with FIG. 10.

The UAV 1150 also include power supply 1178, such as a battery. Theinstructions 1168, when executed by the processors 1172, may help reducedrain on the power supply 1178. For example, for packets received from auser end terminal, the UAV 1150 determines whether a signal quality ofits links to coupled devices meets or exceeds a predetermined threshold.It may further determine whether link capacity exceeds a threshold. Ifboth of these are true, the UAV 1150 sends soft decision bits having areduced width from its modem to its formatter, bypassing FECencoding/decoding. Bypassing the FEC encoding/decoding reduces a drainon the power supply 1178 that would typically result from performing theFEC encoding/decoding at the UAV. Instead, FEC decoding is moved to thegateway terminal, where power resources are better available. Whenpackets are received from the gateway terminal and destined for an endterminal, the UAV 1150 determines whether the packets are tagged for FECbypass, and send the packets accordingly.

In addition to the foregoing, methods according to the presentdisclosure are now described. While operations of the methods aredescribed in a particular order, it should be understood that the orderof operations may be varied. Some operations may be performedsimultaneously. Additionally, operations may be added or omitted.

FIG. 12 illustrates an example flow diagram of a method 1200 oftransmitting packets in a forward direction. In block 1205, the gatewayterminal monitors signal quality of one or more links. For example, alllinks between the gateway, UAV, and end terminal may be monitored. Inother examples, only particular links may be monitored. The monitoringmay be performed continually, periodically, or in response to apredetermined event. For example, when the system is initialized, it maywait a few seconds or minute before beginning monitoring every fewseconds, and send packets for regular processing during that wait time.In other examples, the monitoring may be performed in response toreceipt of one or more packets. In performing the monitoring, thegateway terminal may receive information from the UAV, which may alsoperform monitoring, or from any other coupled device.

In block 1210, the gateway terminal receives a packet from a backhaul,which may be coupled to the gateway by optical fiber or other links. Thepacket may be formatted and sent using any of a variety of protocols.

In block 1215, it is determined whether the signal quality beingmonitored exceeds the predetermined threshold. If not, the packet isencoded for regular UAV processing (block 1230), including FECencoding/decoding in the UAV.

If the signal quality does exceed the threshold, however, the packet isencoded for the link between the UAV and the end terminal (block 1220),such that it may be decoded directly by the end terminal. The encodedpacket is tagged and formatted (block 1225) to identify how it should behandled by the UAV. For example, one or more flags in a header of thepacket may be set to indicate that FEC should be bypassed in the UAV.Moreover, a particular user link over which the packet should be sent bythe UAV may also be indicated in the packet header.

However, regardless of whether the packet is encoded at the gateway, itis sent to the UAV in block 1235. In block 1240, the UAV receives andidentifies the packet. The UAV determined (block 1245) based on theidentification whether the packet is tagged for FEC bypass. If so, theUAV bypasses FEC (block 1260), for example by sending the packet on alink that bypasses an FEC encoder and decoder in the UAV.

If it is determined in block 1245 that the packet is not tagged for FECbypass, regular FEC decoding and encoding for the end terminal link maybe performed at the UAV. Regardless of how the packet is processed atthe UAV, it is sent to the UE in block 1265.

FIG. 13 provides another flow diagram illustrating a method 1300 forsending packets in a receive direction. In block 1305, the UAV monitorssignal quality. Similar to above, the monitoring may be continual,periodic, responsive to particular events, etc. In some examples, suchmonitoring may include receiving information from the gateway or otherdevices coupled to the UAV.

The UAV receives a packet from the end terminal (block 1310), anddetermines whether signal quality is greater than the predeterminedthreshold (block 1315). In some examples, the threshold set in thetransmit direction may be different than the threshold set in thereceive direction. If the signal quality is below the threshold, the UAVperforms typical FEC decoding and encoding in block 1350. However, ifthe signal quality meets the threshold, the UAV may bypass FECencoding/decoding and instead prepare the packet for processing by thegateway. For example, the UAV may determine whether a capacity of thelink between the UAV and the gateway is above a capacity threshold. Ifnot, a modem in the UAV sends raw samples to a formatter (block 1340).If the gateway link has sufficient capacity, however, the modem sendssoft decision bits (block 1325). These soft decision bits may be sentthrough a bit width reducer (block 1330) prior to being sent to theformatter and tagger (block 1335).

In block 1355 the packet is sent to the gateway. The gateway mayidentify the packet in block 1360 and determine, based on theidentification, whether the packet was encoded at the UAV or not (block1365). If it was, regular FEC decoding may be performed by a first FECdecoder in block 1375. However, if FEC decoding/encoding was bypassed atthe UAV, the packet may be sent to a second decoder (block 1370) for FECdecoding. The decoded packet is sent to backhaul at block 1380.

While the above examples are described primarily in relation to UAVs,the power saving techniques described may be implemented in any of avariety of systems where the relay node is located at a remote locationwith limited power. For example, such techniques may be implemented in asatellite, a UAV, a terrestrial site that is power limited, or any othercommunication system.

Because power consumption of a communications payload determines anumber of users that can be supported on the UAV, conserving power inthe UAV using FEC bypass, when available, results in an increased numberof users. The number of users directly translates to the total revenuegenerated by the UAV. Moreover, a lower power payload could reduce thesize of the UAV needed to reach a given set of users.

As these and other variations and combinations of the features discussedabove can be utilized without departing from the subject matter definedby the claims, the foregoing description of the embodiments should betaken by way of illustration rather than by way of limitation of thesubject matter defined by the claims. As an example, the precedingoperations do not have to be performed in the precise order describedabove. Rather, various steps can be handled in a different order orsimultaneously. Steps can also be omitted unless otherwise stated. Inaddition, the provision of the examples described herein, as well asclauses phrased as “such as,” “including” and the like, should not beinterpreted as limiting the subject matter of the claims to the specificexamples; rather, the examples are intended to illustrate only one ofmany possible embodiments. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

The invention claimed is:
 1. A method of improving communications,comprising: receiving a first packet at a gateway communicativelycoupled to an end terminal through an unmanned air vehicle (UAV),wherein a first wireless link communicatively couples the gateway to theUAV, and a second wireless link communicatively couples the UAV to theend terminal; determining, with one or more processors, a signal qualityon at least the first link between the gateway and the UAV in a firstdirection; when the signal quality exceeds a first predeterminedthreshold: encoding, at the gateway, the first received packet forprocessing by the end terminal; tagging the first received packet withan indicator to bypass forward error correction (FEC) at the UAV;monitoring, with the one or more processors at the gateway, the signalquality on at least the first link; comparing the monitored signalquality to a second threshold lower than the first threshold; and whenthe monitored signal quality falls below the second threshold lower,encoding, at the gateway, the first received packets for processing bythe UAV.
 2. The method of claim 1, further comprising: receiving, at thegateway, a second packet from the UAV, the second packet originatingfrom the end terminal; determining, with the one or more processors,whether the second packet was FEC decoded and encoded at the UAV; andwhen it is determined that the second packet was not FEC decoded andencoded at the UAV, decoding the second packet at the gateway using endterminal modem processing.
 3. The method of claim 1, wherein determiningthe signal quality comprises determining an aggregate signal quality onthe first link and the second link.
 4. The method of claim 1, whereindetermining the signal quality comprises computing at least one ofsignal strength, frame error rate, and bit error rate.
 5. The method ofclaim 1, wherein tagging the received packet further comprisesindicating a particular user link on which the UAV is to transmit thereceived packet to the end terminal.
 6. The method of claim 1, furthercomprising continuing encoding and tagging packets for FEC bypass at theUAV until the monitored signal quality falls below the second threshold.7. A gateway, comprising: an interface configured to be communicativelycoupled with an unmanned air vehicle (UAV) over a first link and with atleast one end terminal over a second link between the UAV and the atleast one end terminal; at least one forward error correction (FEC)encoder configured to be interfaced with a backhaul and to receive afirst packet from the backhaul; a formatting unit coupled to the FECencoder; and a controller communicatively coupled to the at least oneFEC encoder and the formatting unit; wherein the controller isconfigured to determine whether a signal quality over the first linkexceeds a first predetermined threshold; wherein when the signal qualityis determined to exceed the first predetermined threshold, the gatewayswitches from a first mode with the first received packet encoded fordecoding by the UAV to a second mode, wherein in the second mode: the atleast one FEC encoder is configured to encode the received first packetfor processing by the end terminal; and the formatting unit isconfigured to tag the received first packet with an indicator to bypassFEC at the UAV; and wherein: when the gateway is in the second mode, thegateway monitors whether the signal quality falls below a secondthreshold lower than the first threshold; and when the signal qualityfalls below the second threshold, the gateway switches back to the firstmode, wherein the first received packet is encoded for decoding by theUAV.
 8. The gateway of claim 7, wherein the formatting unit is furtherconfigured to identify a particular end terminal link, from a pluralityof end terminal links between the UAV and a plurality of end terminals,over which the first packet should be sent.
 9. The gateway of claim 8,wherein in tagging the first packet and in identifying the particularend terminal link, the formatting unit modifies a header of the firstpacket.
 10. The gateway of claim 7, wherein the signal quality iscomputed based on both the first link and the second link.
 11. Thegateway of claim 10, wherein the signal quality is computed as afunction of at least one of signal strength, bit error rate, and frameerror rate.
 12. The gateway of claim 7, wherein: the interface isconfigured to receive at least one second packet from the UAV over thefirst link; the formatting unit is configured to determine whether thesecond packet was decoded and encoded at the UAV; and the controller isconfigured to select one of a first decoder and a second decoder fordecoding the second packet based on the determination by the formattingunit.
 13. The gateway of claim 7, wherein the gateway remains in thesecond mode until the monitored signal quality falls below the secondthreshold.
 14. An unmanned air vehicle (UAV), comprising: a firstinterface configured for receiving a first packet from a gatewaycommunicatively coupled to the UAV via a first wireless link; a secondinterface configured for receiving a second packet from an end terminalcommunicatively coupled to the UAV via a second wireless link; a forwarderror correction (FEC) encoder coupled between the first interface andthe second interface; a FEC decoder coupled between the first interfaceand the second interface; a bypass link coupled between the firstinterface and the second interface and bypassing the FEC encoder and theFEC decoder; and a controller in communication with at least the firstinterface and the second interface, the controller configured to:determine whether the first packet has been encoded for end terminalprocessing; and cause the first packet to be sent on the bypass linkwhen it has been determined that the first packet has been encoded forend terminal processing.
 15. The UAV of claim 14, wherein the controlleris further configured to: determine a signal quality over at least oneof the first and second wireless links; and if the signal qualityexceeds a predetermined threshold, cause the second packet to be sent onthe bypass link.
 16. The UAV of claim 15, wherein determining the signalquality comprises computing an indicator based on at least one of signalstrength, bit error rate, and frame error rate.
 17. The UAV of claim 15,further comprising a formatting unit programmed to format the firstpacket for FEC decoding at the gateway when the first packet is sent onthe bypass link.
 18. The UAV of claim 17, wherein the controller isfurther configured to: determine a capacity of the first wireless link;and if the capacity exceeds a predetermined capacity threshold, sendsoft decision bits of the packet to the formatting unit.
 19. The UAV ofclaim 18, further comprising a bit width reducer coupled between thesecond interface and the formatting unit, the bit width reducerconfigured to reduce a width of the soft decision bits.
 20. The UAV ofclaim 18, wherein if the capacity of the second wireless link does notexceed the capacity threshold, the controller is configured to send rawsamples to the formatting unit.